The method and apparatus described herein relates generally to removing a coil from a slot of a dynamoelectric machine. More specifically, the method and apparatus relates to the use of a wedge shaped member to remove the coil from the slot.
A typical motor is comprised of an armature that rotates within a fixed stator. The stator includes a core of stacked, insulated, iron laminations, with windings (or coils) of insulated copper conductors that fill slots in the core. In some motors the windings (or coils) are vacuum pressure impregnated (VPI) into the slots. This method results in a very secure installation method. Unfortunately, the VPI method also makes removal of the windings difficult and potentially problematic.
Motors may fail for various reasons. One typical cause is the degradation of the stator winding insulation. This degradation may be caused by repeated motor overheating, extreme one-time heating (possibly caused by loss of one of the three electrical phases), or water entering the motor. Normally, failure due to breakdown of stator winding insulation does not damage the core, and the core can be salvaged and rewound (and subsequently reused) if the old winding is carefully removed.
One known method for removing the windings from the stator includes attaching a strap or chain to the end of a winding, and then pulling on the winding to remove it. This approach has the potential to damage the core, as an “even” pull cannot always be guaranteed. The chain or strap used to pull on the winding may also break due to the extreme stress, and this can potentially create a hazardous condition for nearby workers. Another known method employs a large oven to heat and “burn-out” the windings. This approach creates environmental concerns and uses a large amount of energy. In addition, the high temperatures required also negatively affect the stator core and reduce the number of times it may be rewound.
It would be desirable, if a safer, environmentally friendly, less damaging and more economical method could be found for removing windings from a slot without damaging the core.